1. Field of the Invention
The present invention relates to a camphor-derived compound, a method for manufacturing the same, and an application thereof and, more particularly, to a camphor-derived compound used as a chiral catalyst, a method for manufacturing the same, and an application to catalyze asymmetric addition of an organic zinc to an aldehyde using the same.
2. Description of Related Art
When an enzyme performs catalysis in an organism, owing to its specific conformation in the structure, it can differentiate between two enantiomers having contrary chirality and catalyze only one in a specific configuration. Accordingly, a small difference in a chiral center of enantiomers can cause entirely different to even completely contrary physiological reactions or symptoms, and some examples are demonstrated as follows. Firstly, referring to glucoses in food, dextroglucose
tastes sweet and can be ingested to afford energy in a human body. Although levoglucosan
also tastes sweet, it can not be ingested and will be excreted outside the human body. Secondly, in regard to carvone used as flavor additives, S-form carvone
has a flavor of cilantro but R-form
has a flavor of mint. Thirdly, with regard to a common amino acid asparagine, S-form asparagine
tastes bitter, but R-form asparagine
tastes sweet. Fourthly, with relation to a medicine Dopa, S-form dopa
is widely used as a medicine for treatment of Parkinson's disease, but R-form dopa
is a poison causing osteoporosis. Fifthly, in relation to a medicine Naproxen, S-form naproxen
is an anti-inflammative anodyne having sustaining efficacy, but R-form naproxen
can cause serious damage to kidneys.
However, in common syntheses, S-form and R-form enantiomers are simultaneously produced. If the enantiomers need to be used in an organism, syntheses or purification are required to isolate one enantiomer having high optical activity and single configuration.
Among methods for obtaining a pure compound with specific chirality, asymmetric synthesis is the most applicative and potential method. In this method, a chiral compound is used to provide a source of chirality so that the reactant forms an asymmetric plane to induce asymmetric reaction. Such method can be classified into three types: (A) chiral reagent: a reactant is asymmetrically reacted with a chiral reagent formed of chiral molecules; (B) chiral auxiliary: a reactant is combined to a chiral molecule to form an asymmetric plane so as to react with other reagents and the chiral auxiliary can be retrieved after the reaction; and (C) chiral catalyst: a chiral molecule and a reactant or reagent form an intermediate having high reactivity for asymmetric reaction, and a large amount of a product having optical activity can be obtained in the presence of a small amount of the chiral catalyst.
Since secondary alcohols having optical activity exist commonly in the structure of many natural products and drugs (for example, Orphenadrine, Neobenodine, Carbinoxamine, Efavirenz, Fostriencin, and Camptothecin), how to synthesize such secondary alcohols becomes an important topic. Currently, methods for constructing chiral centers in secondary alcohols can be classified into three types: (A) asymmetric reduction of ketones; (B) open-ring reaction of chiral epoxy compounds; and (C) asymmetric addition of metal nucleophilic reagents to aldehydes.
In the methods delineated above, metal zinc has low price, cytotoxicity, and effects to a human body, and thus is appropriate for catalysis. In asymmetric addition of organic zincs to aldehydes, catalysis performed by proper chiral catalysts is potential to give secondary alcohols having high optical activity.